Vehicle radar sensing system with surface segmentation using interferometric statistical analysis

ABSTRACT

A sensing system for a vehicle includes at least one radar sensor disposed at the vehicle and having a field of sensing exterior of the vehicle. The at least one radar sensor includes multiple transmitting antennas and multiple receiving antennas. The transmitting antennas transmit signals and the receiving antennas receive the signals reflected off objects. Radar data sensed by the at least one radar sensor is received at a control, and a vehicle motion estimation is received at the control and processed at a processor of the control. The control, responsive at least in part to processing at the processor of the received sensed radar data and the received vehicle motion estimation, determines different types of surfaces in the field of sensing of the at least one radar sensor.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims the filing benefits of U.S. provisionalapplication Ser. No. 62/555,223, filed Sep. 7, 2017, which is herebyincorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates generally to a vehicle sensing system fora vehicle and, more particularly, to a vehicle sensing system thatutilizes one or more sensors at a vehicle to provide a field of sensingat or around the vehicle.

BACKGROUND OF THE INVENTION

Use of imaging sensors or ultrasonic sensors or radar sensors in vehiclesensing systems is common and known. Examples of such known systems aredescribed in U.S. Pat. Nos. 8,013,780 and 5,949,331 and/or U.S.publication No. US-2010-0245066 and/or International Publication No. WO2011/090484, which are hereby incorporated herein by reference in theirentireties.

SUMMARY OF THE INVENTION

The present invention provides a driver assistance system or sensingsystem for a vehicle that utilizes a sensor module or system disposed atthe vehicle and comprising at least one radar sensor disposed at thevehicle and having a field of sensing exterior of the vehicle. The atleast one radar sensor comprises multiple transmitting (Tx) antennas(transmitters) and receiving (Rx) antennas (receivers) to provide highdefinition, fine resolution in azimuth and/or elevation to determinehigh definition radar reflection responses for objects and surfacesdetected by the system. The system includes a control, where outputs(such as radar data acquisitions of multiple scans) of the at least oneradar sensor are communicated to the control, and where the control,responsive to the outputs of the at least one radar sensor, determinesdifferent types of surfaces at or near the equipped vehicle or on whichthe equipped vehicle is traveling. The system also detects the presenceof one or more objects exterior the vehicle and within the field ofsensing of at least one of the at least one radar sensor.

The control of the sensing system receives radar data sensed by at leastone radar sensor (such as radar data of multiple consecutive scans) andreceives a vehicle motion estimation. The control, responsive toreceived vehicle motion estimation and received sensed radar data (whichis time stamped so that it can be correlated with the vehicle motion),determines the type of surface on and along which the vehicle istraveling.

The present invention provides a means to segment and distinguishdifferent kind of surfaces seen by an automotive radar. Differentsurfaces present different scattering properties. Data acquired fromconsecutive scans can be used to coherently analyze the statisticalproperties of different range-angle cells corresponding to stationaryobjects. The cells sharing similar statistical properties can beclustered together. In this way, the range-angle imaging correspondingto stationary objects can be segmented. This technique is useful todistinguish the road and its path from the surroundings (such as a dirtshoulder along the side of the road) using automotive radar.

These and other objects, advantages, purposes and features of thepresent invention will become apparent upon review of the followingspecification in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a vehicle with a sensing system thatincorporates a radar sensor in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A vehicle sensing system, such as a driver assist system, objectdetection system, parking assist system and/or alert system, operates tocapture sensing data exterior of the vehicle and may process thecaptured data to detect objects or other vehicles at or near theequipped vehicle and in the predicted path of the equipped vehicle, suchas to assist a driver of the equipped vehicle in maneuvering the vehiclein a forward or rearward direction or to assist the driver in parkingthe vehicle in a parking space. The system includes a processor that isoperable to receive sensing data from one or more sensors and to providean output to a control that, responsive to the output, generates analert or controls an accessory or system of the vehicle, or highlightsor overlays an alert on a display screen (that may be displaying videoimages captured by a single rearward viewing camera or multiple camerasproviding forward, side or 360 degree surround views of the areasurrounding the vehicle during a reversing or low speed maneuver of thevehicle).

Referring now to the drawings and the illustrative embodiments depictedtherein, a vehicle 10 includes an driver assistance system or sensingsystem 12 that includes at least one radar sensor unit, such as aforward facing radar sensor unit 14 (and the system may optionallyinclude multiple exterior facing sensors, such as multiple exteriorfacing radar sensors or cameras or other sensors, such as a rearwardfacing sensor at the rear of the vehicle, and a sideward/rearward facingsensor at respective sides of the vehicle), which sense regions exteriorof the vehicle. The sensing system 12 includes a control or electroniccontrol unit (ECU) or processor that is operable to process datacaptured by the sensor or sensors and may detect objects or the like.The data transfer or signal communication from the sensor to the ECU maycomprise any suitable data or communication link, such as a vehiclenetwork bus or the like of the equipped vehicle.

Some automotive radars use MIMO (Multiple Input Multiple Output)techniques to create an effective virtual antenna aperture, which issignificantly larger than the real antenna aperture, and delivers muchbetter angular resolution than conventional radars, such as, forexample, conventional scanning radars.

Algorithms for automotive radar that estimate road surfaces and freespace are typically based on target detection lists. The algorithmscreate clusters by grouping targets that are close to each other andtaking into account their accuracies. This presents several limitations,such as sparsity to identify surfaces or the fact that there is noproper scattering mechanism analysis present in the algorithms. Thesystem of the present invention deals with images related to non-movingobjects. The images are naturally oriented to better identify surfaces.In addition, the system of the present invention is oriented to workwith amplitudes and phases. Therefore, the system presents a morerefined and robust statistical analysis than using only points astypical algorithms use.

The system of the present invention segments different kind of surfacesseen by an automotive radar by using the scattering properties ofdiffering surfaces. The system receives as input an ego motionestimation (that estimates the motion of a sensor disposed at thesubject or equipped vehicle), a complex (phase and amplitude)acquisition or image for at least two consecutive scans of the radarsystem, a time stamp for each acquisition, and a sensor position of thesensor with respect to the vehicle. Each of the images is dedicated tonon-moving objects, and can be either two dimensional (2D) or threedimensional (3D). The dimensions in the case of a 2D acquisition includeRange and Angle, while the dimensions in the case of having a volume(3D) include Range, Azimuth Angle and Elevation Angle. Optionally, theimage may be provided in Cartesian coordinates.

During operation, the images from different scans are coregistered. Tocoregister the images, one image is taken as a reference and the rest ofthe images are transformed such that every pixel/voxel of the imagerefers to the same physical space as the pixels/voxels of the referenceimage. This coregistration may vary along the image. The displacement ofthe car (determined based on ego-motion and time stamp) is taken intoaccount. A fine coregistration may be performed based on point-liketargets or distributed targets or a mix of both, depending on the scenenature.

The set of images can be paired generating interferograms. In otherwords, pairing images by multiplying one coregistered image by theconjugate of another image. The scans can be paired in different ways,such as, for example, pairing consecutive scans in order to minimize thedecorrelation and the amount of data.

The next step is to “flatten” the interferometric phase by taking intoaccount a first model of a terrain model. When there is a terrain modelavailable, it is possible to generate its synthetic phase and subtractit from the previously obtained interferometric phase. In cases wherethere is not a terrain model, it is possible to generate thecorresponding interferograms for a flat surface, taking into account thesensor position on the scans.

The system of the present invention can carry on a statistical analysisthat takes into account amplitudes and phases for the differentrg-angle(s) interferometric cells. The cells showing similar statisticalproperties will be clustered together. Different kinds ofinterferometric analysis can be performed, such as Region Growing,Amplitude-Phase driven filters, Non-Local filters, and/or the like. Inthis way, the system determines a surface segmentation based on asurface scattering mechanism. The system can thus determine anddistinguish a road surface from a non-road surface, such as a dirtshoulder by the road, so that the system can assist in determining ormaintaining a path of travel of the vehicle along the road.

Thus, the sensing system of the present invention segments differentkinds of surfaces sensed or seen by an automotive radar. The system isbased on the fact that different surfaces present different scatteringproperties. Data acquired from consecutive scans can be used by thesensing system to coherently analyze the statistical properties ofdifferent range-angle cells corresponding to stationary objects. Thecells sharing similar statistical properties may be clustered together.In this way, the range-angle imaging corresponding to stationary objectsmay be segmented. This technique is useful for distinguishing the roadand its path from the surroundings using automotive radar.

The system may provide an output for a driving assist system of thevehicle, such as one or more of (i) automated parking, (ii) blind spotdetection, (iii) cross traffic alert, (iv) lane change assist, (v) lanemerge assist, (vi) automatic emergency braking, (vii) pedestriandetection, (viii) turn assist, (ix) terrain management, (x) collisionmitigation and (xi) intersection collision mitigation. Optionally, theoutput may be provided to an autonomous vehicle control system.

For autonomous vehicles suitable for deployment with the system of thepresent invention, an occupant of the vehicle may, under particularcircumstances, be desired or required to take over operation/control ofthe vehicle and drive the vehicle so as to avoid potential hazard for aslong as the autonomous system relinquishes such control or driving. Suchoccupant of the vehicle thus becomes the driver of the autonomousvehicle. As used herein, the term “driver” refers to such an occupant,even when that occupant is not actually driving the vehicle, but issituated in the vehicle so as to be able to take over control andfunction as the driver of the vehicle when the vehicle control systemhands over control to the occupant or driver or when the vehicle controlsystem is not operating in an autonomous or semi-autonomous mode.

Typically an autonomous vehicle would be equipped with a suite ofsensors, including multiple machine vision cameras deployed at thefront, sides and rear of the vehicle, multiple radar sensors deployed atthe front, sides and rear of the vehicle, and/or multiple lidar sensorsdeployed at the front, sides and rear of the vehicle. Typically, such anautonomous vehicle will also have wireless two way communication withother vehicles or infrastructure, such as via a car2car (V2V) or car2xcommunication system. The forward viewing camera and/or the sensor ofthe lane determining system may comprise one of the cameras and/or oneof the sensors of the autonomous vehicle control system.

The sensing system may include a machine vision system (comprising atleast one exterior viewing camera disposed at the vehicle and an imageprocessor for processing image data captured by the at least onecamera), where information is shared between the stereo radar and themachine vision system.

The system may include two or more individual radars, having individualor multiple Tx (transmitters) and Rx (receivers) on an antenna array,and may utilize aspects of the systems described in U.S. Pat. Nos.9,753,121; 9,689,967; 9,599,702; 9,575,160; 9,146,898; 9,036,026;8,027,029; 8,013,780; 6,825,455; 7,053,357; 7,408,627; 7,405,812;7,379,163; 7,379,100; 7,375,803; 7,352,454; 7,340,077; 7,321,111;7,310,431; 7,283,213; 7,212,663; 7,203,356; 7,176,438; 7,157,685;6,919,549; 6,906,793; 6,876,775; 6,710,770; 6,690,354; 6,678,039;6,674,895 and/or 6,587,186, and/or International Publication Nos. WO2018/007995 and/or WO 2011/090484, and/or U.S. Publication Nos.US-2018-0231635; US-2018-0045812; US-2018-0015875; US-2017-0356994;US-2017-0315231; US-2017-0276788; US-2017-0254873; US-2017-0222311and/or US-2010-0245066, which are hereby incorporated herein byreference in their entireties.

Changes and modifications in the specifically described embodiments canbe carried out without departing from the principles of the invention,which is intended to be limited only by the scope of the appendedclaims, as interpreted according to the principles of patent lawincluding the doctrine of equivalents.

1. A sensing system for a vehicle, said sensing system comprising: atleast one radar sensor disposed at a vehicle equipped with said sensingsystem and having a field of sensing exterior of the equipped vehicle;wherein said at least one radar sensor comprises multiple transmittingantennas and multiple receiving antennas, wherein said transmittingantennas transmit signals and said receiving antennas receive thesignals reflected off objects; a control comprising a processor, whereinradar data sensed by said at least one radar sensor is received at saidcontrol and processed at said processor; wherein a vehicle motionestimation is received at said control; and wherein said control,responsive at least in part to processing at the processor of thereceived sensed radar data and the received vehicle motion estimation,determines different types of surfaces in the field of sensing of saidat least one radar sensor.
 2. The sensing system of claim 1, whereinsaid at least one radar sensor is disposed at a front portion of theequipped vehicle and senses forward of the equipped vehicle.
 3. Thesensing system of claim 2, wherein said control, responsive at least inpart to processing at the processor of the received sensed radar data,distinguishes a surface of a road along which the equipped vehicle istraveling from a non-road surface adjacent to the road.
 4. The sensingsystem of claim 1, wherein the received sensed radar data comprisesradar data images for at least two consecutive scans by said at leastone radar sensor.
 5. The sensing system of claim 4, wherein said radardata acquisitions comprise two dimensional radar data images.
 6. Thesensing system of claim 4, wherein said radar data acquisitions comprisethree dimensional radar data images.
 7. The sensing system of claim 4,wherein each radar data image is time stamped.
 8. The sensing system ofclaim 7, wherein said control coregisters images from different scans.9. The sensing system of claim 8, wherein the images from differentscans can be paired to generate interferograms by multiplying acoregistered image by the conjugate of another image.
 10. The sensingsystem of claim 1, wherein said control, responsive at least in part toprocessing at the processor of the received sensed radar data and thereceived vehicle motion estimation, analyzes statistical properties ofrange-angle cells corresponding to stationary objects.
 11. The sensingsystem of claim 10, wherein said control clusters range-angle cells withsimilar statistical properties together.
 12. The sensing system of claim11, wherein said control segments the different types of surfaces. 13.The sensing system of claim 1, wherein said control, responsive toprocessing at the processor of the received sensed radar data, detectsthe presence of one or more objects exterior the equipped vehicle andwithin the field of sensing of said at least one radar sensor.
 14. Thesensing system of claim 1, wherein a vision system of the equippedvehicle comprises at least one exterior viewing camera disposed at theequipped vehicle and an image processor for processing image datacaptured by the at least one camera, and wherein information is sharedbetween said sensing system and the vision system of the equippedvehicle.
 15. The sensing system of claim 1, wherein said sensing systemcomprises two or more individual radar sensors, each having multipletransmitting antennas and receiving antennas on an antenna array, andwherein information is shared between the individual radars operating instereo to determine high definition radar reflection responses forobject detection by said sensing system.
 16. The sensing system of claim1, wherein said sensing system provides an output for at least onedriving assist system function selected from the group consisting of (i)automated parking, (ii) blind spot detection, (iii) cross traffic alert,(iv) lane change assist, (v) lane merge assist, (vi) automatic emergencybraking, (vii) pedestrian detection, (viii) turn assist, (ix) terrainmanagement, (x) collision mitigation and (xi) intersection collisionmitigation.
 17. A sensing system for a vehicle, said sensing systemcomprising: at least one radar sensor disposed at a vehicle equippedwith said sensing system and having a field of sensing exterior of theequipped vehicle; wherein said at least one radar sensor comprisesmultiple transmitting antennas and multiple receiving antennas, whereinsaid transmitting antennas transmit signals and said receiving antennasreceive the signals reflected off objects; a control comprising aprocessor, wherein radar data sensed by said at least one radar sensoris received at said control and processed at said processor; wherein thereceived sensed radar data comprises radar data images for at least twoconsecutive scans by said at least one radar sensor; wherein a vehiclemotion estimation is received at said control; wherein said control,responsive at least in part to processing at the processor of thereceived sensed radar data and the received vehicle motion estimation,determines different types of surfaces in the field of sensing of saidat least one radar sensor; wherein said control, responsive at least inpart to processing at the processor of the received sensed radar data,distinguishes a surface of a road along which the equipped vehicle istraveling from a non-road surface adjacent to the road; and wherein saidsensing system provides an output for at least one driving assist systemfunction selected from the group consisting of (i) automated parking,(ii) blind spot detection, (iii) cross traffic alert, (iv) lane changeassist, (v) lane merge assist, (vi) automatic emergency braking, (vii)pedestrian detection, (viii) turn assist, (ix) terrain management, (x)collision mitigation and (xi) intersection collision mitigation.
 18. Thesensing system of claim 17, wherein said control coregisters images fromdifferent scans, and wherein the images from different scans can bepaired to generate interferograms by multiplying a coregistered image bythe conjugate of another image.
 19. The sensing system of claim 17,wherein said control segments the different types of surfaces.
 20. Asensing system for a vehicle, said sensing system comprising: at leastone radar sensor disposed at a vehicle equipped with said sensing systemand having a field of sensing exterior of the equipped vehicle; whereinsaid at least one radar sensor is disposed at a front portion of theequipped vehicle and senses forward of the equipped vehicle; whereinsaid at least one radar sensor comprises multiple transmitting antennasand multiple receiving antennas, wherein said transmitting antennastransmit signals and said receiving antennas receive the signalsreflected off objects; a control comprising a processor, wherein radardata sensed by said at least one radar sensor is received at saidcontrol and processed at said processor; wherein a vehicle motionestimation is received at said control; wherein said control, responsiveat least in part to processing at the processor of the received sensedradar data and the received vehicle motion estimation, determinesdifferent types of surfaces in the field of sensing of said at least oneradar sensor; wherein said control coregisters images from differentscans, and wherein the images from different scans can be paired togenerate interferograms by multiplying a coregistered image by theconjugate of another image; wherein said control, responsive toprocessing at the processor of the received sensed radar data, detectsthe presence of one or more objects exterior the equipped vehicle andwithin the field of sensing of said at least one radar sensor; andwherein said sensing system provides an output for at least one drivingassist system function selected from the group consisting of (i)automated parking, (ii) blind spot detection, (iii) cross traffic alert,(iv) lane change assist, (v) lane merge assist, (vi) automatic emergencybraking, (vii) pedestrian detection, (viii) turn assist, (ix) terrainmanagement, (x) collision mitigation and (xi) intersection collisionmitigation.
 21. The sensing system of claim 20, wherein said control,responsive at least in part to processing at the processor of thereceived sensed radar data, distinguishes a surface of a road alongwhich the equipped vehicle is traveling from a non-road surface adjacentto the road.
 22. The sensing system of claim 20, wherein said control,responsive at least in part to processing at the processor of thereceived sensed radar data and the received vehicle motion estimation,analyzes statistical properties of range-angle cells corresponding tostationary objects, and wherein said control clusters range-angle cellswith similar statistical properties together, and wherein said controlsegments the different types of surfaces.